1. Field of the Invention
The present invention relates to semiconductor devices and methods of fabricating semiconductor devices, and more particularly, to image sensor devices and methods of fabricating image sensor devices.
2. Description of the Related Art
An image sensor is an apparatus that acquires an image using a light sensitive semiconductor device. In particular, some semiconductor devices have certain properties that react to external energy, such as energy from photons. Light reflected/emitted by any object present in nature has a unique energy characterized by its wavelength. An image sensor receives light reflected/emitted by an object through a filter of a pixel unit, and transforms the light energy into an electrical signal using a photodiode (PD) or other light-sensitive semiconductor device disposed within the image sensor.
FIGS. 1A and 1B are respectively a cross-sectional view and a plan view illustrating a conventional image sensor device.
Referring to FIGS. 1A and 1B, the image sensor device includes a light receiving unit 10, a pixel metal wire layer 20, a filter unit 30, and a lens unit 40. The light receiving unit 10 includes a plurality of photodiodes or other light sensitive semiconductor devices that transform detected light energy into an electrical signal. The pixel metal wire layer 20 includes a transparent material, for example, silicon oxide (SiO2), and includes multi-layered metal wires 22 between pixels.
The filter unit 30 includes color filters 32, that is, regularly arranged red, blue, and green color filters, which receive and transmit light of corresponding wavelengths. As depicted in FIGS. 1A and 1B, the filter unit 30 is divided into an active pixel region A that receives light and an optical black pixel region B. In the optical black pixel region B, light is substantially prevented from reaching the light receiving unit 10. Therefore, the signal output by the light receiving unit 10 in the optical black region B can provide a standard with respect to a “black” signal (i.e. the absence of light). Resin layers 34 and 36 for planarizing the image sensor device are generally formed above and below the color filters 32.
As illustrated in FIG. 1B, the filters of the optical black pixel region B are formed using color filters 32 having the same arrangement as those in the active pixel region A. Referring to FIG. 1A, a layer 24 for blocking light is formed in the pixel metal wire layer 20 in a lower part of the optical black pixel region B. That is, a top metal layer 24 is formed in an upper part of the pixel metal wire layer 20 to block/reflect light entering into the optical black pixel region B through the lens unit 40.
In a conventional image sensor device, due to the presence of the top metal layer 24 in the optical black pixel region B, the overall thickness of the image sensor device is increased by as much as the thickness of the top metal layer 24. In addition, due to the presence of the top metal layer 24, some electrical characteristics of the optical black pixel region B can differ from those of the active pixel region A. That is, in order to improve the dark and/or noise characteristics of the light receiving unit 10, an annealing process, such as a hydrogen passivation process, is generally performed after the pixel metal wire layer 20 is formed. However, it can be difficult to apply the hydrogen passivation process to the optical black pixel region B due to the presence of the top metal layer 24. As a result, the electrical characteristics of the light receiving unit 10 in the optical black pixel region B can differ from those of the light receiving unit 10 in the active pixel region A.